KEF M400RB M400 Hi-Fi On-Ear Headphones - Racing Blue The M400's frame is engineered for comfort and portability, with its easy-to-use folding capabilities, comfortable noise-isolating ear pads, and a cushioned headband. Take all your calls hands free with the M400's integrated in-line microphone, which also allows you to operate the play functions of your audio or switch between calls and music. The KEF M400 utilizes an ultra-light 1.5 inch neodymium driver and copper clad aluminum wire voice coil in order to best portray your favorite artist's original performance. The M400 is structured so that its aluminum frame applies just the right amount of pressure for the headphones to sit comfortably on you head without becoming irritating. The KEF M400 headphones fold up to fit snugly into a softshell carrying pouch and its cable detaches, making it perfect for safe storage and easy traveling.